
package com.shiku.imserver.common.utils;


public class BASE64Util {

    public static String byteArrayToBase64(byte[] a) {

        return byteArrayToBase64(a, false);

    }


    public static String byteArrayToAltBase64(byte[] a) {

        return byteArrayToBase64(a, true);

    }


    private static String byteArrayToBase64(byte[] a, boolean alternate) {

        int aLen = a.length;

        int numFullGroups = aLen / 3;

        int numBytesInPartialGroup = aLen - 3 * numFullGroups;

        int resultLen = 4 * (aLen + 2) / 3;

        StringBuilder result = new StringBuilder(resultLen);

        char[] intToAlpha = alternate ? intToAltBase64 : intToBase64;


        int inCursor = 0;

        for (int i = 0; i < numFullGroups; i++) {

            int byte0 = a[inCursor++] & 0xFF;

            int byte1 = a[inCursor++] & 0xFF;

            int byte2 = a[inCursor++] & 0xFF;

            result.append(intToAlpha[byte0 >> 2]);

            result.append(intToAlpha[byte0 << 4 & 0x3F | byte1 >> 4]);

            result.append(intToAlpha[byte1 << 2 & 0x3F | byte2 >> 6]);

            result.append(intToAlpha[byte2 & 0x3F]);

        }


        if (numBytesInPartialGroup != 0) {

            int byte0 = a[inCursor++] & 0xFF;

            result.append(intToAlpha[byte0 >> 2]);

            if (numBytesInPartialGroup == 1) {

                result.append(intToAlpha[byte0 << 4 & 0x3F]);

                result.append("==");

            } else {


                int byte1 = a[inCursor++] & 0xFF;

                result.append(intToAlpha[byte0 << 4 & 0x3F | byte1 >> 4]);

                result.append(intToAlpha[byte1 << 2 & 0x3F]);

                result.append('=');

            }

        }


        return result.toString();

    }


    private static final char[] intToBase64 = new char[]{'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'};


    private static final char[] intToAltBase64 = new char[]{'!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':', ';', '<', '>', '@', '[', ']', '^', '`', '_', '{', '|', '}', '~', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '?'};


    public static byte[] base64ToByteArray(String s) {

        return base64ToByteArray(s, false);

    }


    public static byte[] altBase64ToByteArray(String s) {

        return base64ToByteArray(s, true);

    }


    private static byte[] base64ToByteArray(String s, boolean alternate) {

        byte[] alphaToInt = alternate ? altBase64ToInt : base64ToInt;

        int sLen = s.length();

        int numGroups = sLen / 4;

        if (4 * numGroups != sLen) {

            throw new IllegalArgumentException("String length must be a multiple of four. len=" + sLen);

        }

        int missingBytesInLastGroup = 0;

        int numFullGroups = numGroups;

        if (sLen != 0) {

            if (s.charAt(sLen - 1) == '=') {

                missingBytesInLastGroup++;

                numFullGroups--;

            }

            if (s.charAt(sLen - 2) == '=') {

                missingBytesInLastGroup++;

            }

        }

        byte[] result = new byte[3 * numGroups - missingBytesInLastGroup];


        int inCursor = 0, outCursor = 0;

        for (int i = 0; i < numFullGroups; i++) {

            int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);

            int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);

            int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);

            int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);

            result[outCursor++] = (byte) (ch0 << 2 | ch1 >> 4);

            result[outCursor++] = (byte) (ch1 << 4 | ch2 >> 2);

            result[outCursor++] = (byte) (ch2 << 6 | ch3);

        }


        if (missingBytesInLastGroup != 0) {

            int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);

            int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);

            result[outCursor++] = (byte) (ch0 << 2 | ch1 >> 4);


            if (missingBytesInLastGroup == 1) {

                int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);

                result[outCursor++] = (byte) (ch1 << 4 | ch2 >> 2);

            }

        }


        return result;

    }


    private static int base64toInt(char c, byte[] alphaToInt) {

        int result = alphaToInt[c];

        if (result < 0) {

            throw new IllegalArgumentException("Illegal character " + c);

        }

        return result;

    }


    private static final byte[] base64ToInt = new byte[]{-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51};


    private static final byte[] altBase64ToInt = new byte[]{-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, -1, 62, 9, 10, 11, -1, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 17, -1, 18, 19, 21, 20, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 22, 23, 24, 25};

}


